When operation reliability of a swelling CID embedded in a pouch cell within a vehicle is analyzed, it may be seen that operation reliability of the swelling CID depends on a size of the pouch cell, more particularly, a thickness of the pouch cell, due to a design structure of pouch cells which are adhered to a cooling plate in a thickness direction. In other words, when a pouch cell has a substantially thin thickness, a swelling (e.g., expansion) thickness is restricted by the cooling plate. When a pouch cell has a substantially thick thickness, since substantial swelling space is present between the cooling plates, a swelling delay phenomenon may occur.